They don’t call these the “Cascades” for nothing.
There is in most circumstances an abundance of fresh water to find along or nearby NW trails. Regardless of how pristine it looks water should always be purified to avoid the dreaded Beaver Fever (Ghiardia). A Steripen is my favorite method of purifying water that I have retrieved from a Cascade stream or water fall. In situations where there is a lot of sediment in the water a pump or straining through a t-shirt can be a good way to get rid of sediment. Other options are iodine tablets (leave funky taste) Aqua pure chlorine treatment isn’t as bad tasting but takes several minutes of waiting. Hard containers like the traditional aluminum bottles or plastic Nalgine bottles are good for carrying hot liquids camping etc. Otherwise a Camel-back or water bladder will give the easiest access to hydration while you are moving.